he says it's a nationwide problem caused by farm fertilizer runoff. the cure, he says, is convincing farmers to carefully fertilize so nutrients stay on the fields and not in the water. >> otherwise these blooms are going to continue to grow. the human health problems that we see are going to increase. >> reporter: assaulting our senses, our economy, and our health. jim avila, abc news, lake petenwell, wisconsin. >> that is nasty stuff. >> oh, that's an understand statement, but the wisconsin department of natural resources says the best way to treat this is naturally, but they say it could take several years to get rid of it completely. in fact, there was a large amount of -- lake erie, almost a third of the surface, covered. >> cut big time into the fishing industry there. apparently it's in more or less every state. peaks august through september. nearly every state in the union. clearly really bad there. in the great lakes area. >> scientific term, cyano bacteria. >> yeah. >> cyano meaning green for blue? >> right. that's what i heard.